MICROWAVE RECTIFICATION USING QUARTZ.
Physical sciences research papers no. 319,
AIR FORCE CAMBRIDGE RESEARCH LABS L G HANSCOM FIELD MASS
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The linear and nonlinear behavior of a thin piezoelectric quartz disk under microwave-frequency excitation is considered both theoretically and experimentally. A theory developed for X-cut quartz predicts the generation of a dc electric field and a corresponding dc voltage across the disk, owing to second-order coefficients in the piezoelectric constitutive relations. These second-order coefficients are assumed to be the dominant nonlinearities of the system. Temperature effects are neglected. Microwave acoustic resonances corresponding to high harmonics of the fundamental elastic standing wave were observed for X-cut and AC-cut quartz disks, in excellent agreement with the linear theory. Equivalent-circuit methods for description and measurement of these resonances are given. An equivalent circuit describing the nonlinear dc behavior of the disk derived for a simple model. This circuit consists of a voltage source in series with a capacitance. The open-circuit voltage is a product of the second-order coefficients and the square of the magnitude of the applied electric displacement field, and is in addition dependent on the applied microwave frequency. With a simple model used for the external network, the measurable voltage associated with the effect was determined. Direct comparison of theory and experiment was not possible since the model could not be applied to explain several observed effects. Microwave rectification has been achieved, however, by means of both polished and fine-ground X-cut quartz disks placed in the gap of a highly reentrant S-band microwave cavity. Author
- Electrical and Electronic Equipment